Permanent magnet actuated reed switch having adjustable magnet pole pieces



Sept. 17, 1968 R c. MCLAUGHLIN ET AL 3,402,375 7 PERMANENT MAGNETACTUATED REED SWITCH HAVING ADJUSTABLE MAGNET POLE PIECES Filed NOV. 21,1966 TO DISTRlBUTOR FIGS INVENTORSY ROBERT c. McLAUGHLIN T CHARLES E.SHANO ATTORNEYS United States Patent 3,402,375 PERMANENT MAGNET ACTUATEDREED SWITCH HAVING ADJUSTABLE MAGNET POLE PIECES Robert C. McLaughlin,Bloomingdale, and Charles L. Shano, Morton Grove, Iil., assignors toMotorola, Inc., Franklin Park, IlL, a corporation of Illinois Filed Nov.21, 1966, Ser. No. 595,896 6 Claims. (Cl. 335-205) This inventionpertains generally to magnetic switching apparatus and more particularlyto a magnetic reed switch for controlling the current through theignition coil of an internal combustion engine.

Magnetic reed switches have been proposed that have a reed elementforming a movable switch arm which is biased to one of two pole membersor contacts by a permanent magnet coupling the members. A magnetic rotorhaving spaced magnetic poles of alternating polarity is passed in closeproximity to the reed element so that the magnetic fields of the rotorpoles alternately move the reed element between the pole members. In thepast, there have been various problems with this type of switch. Forinstance, the fields of opposite polarity cause the reed element toswitch between the pole members in one direction faster than in theopposite direction. This time difference can be very critical, forinstance, in automobile ignition systems where accurate switching isneeded for proper ignition timing. One method suggested to correct thisproblem is to accurately locate the discrete poles about the peripheryof the magnetic rotor in a spaced relationship so that their fields willcause the reed element to switch between the pole members in bothdirections in exactly the same time. However, the cost involved inaccurately determining where the discrete poles should be located andconstructing the poles integral with the rotor mechanism is relativelyhigh.

It is an object of this application to provide improved magnetic reedswitch apparatus.

It is another object of this invention to provide magnetic reed switchapparatus in which the reed element is switched at a constant ratebetween contacts by each of the poles of the magnetic rotor.

It is a further object of this invention to provide magnetic reed switchapparatus that is relatively inexpensive to manufacture and assemble.

One feature of this invention is magnetic reed switch apparatus having amagnetic rotor including a shaft driven, cylindrical magnet having firstand second oppositely polarized end portions, first and secondrelatively movable pole pieces mounted on said end portions and aplurality of spaced poles inte ral with each pole piece. The first andsecond pole plates are movable relative to one another about the shaftto vary the spacing between the poles of opposite polarity.

Another feature of this invention is magnetic reed switch apparatushaving first and second pole members at least one of which forms aswitch contact and which are positioned to be engaged by a reed elementforming a movable switch arm. A first permanent magnet is coupled acrossthe pole members to bias the same to opposite polarities and a secondpermanent magnet is coupled to the reed element to bias the same to theopposite polarity of one of the first and second pole members so that amagnetic circuit is completed between the one pole member and the reedelement thereby biasing the reed element into contact with the polemember.

In the drawing:

FIG. 1 is a side elevation view partly in cross-section of the magneticreed switch apparatus in accordance with this invention;

FIG. 2 is a plan view of the apparatus of FIG. 1;

FIG. 3 is a side elevation view partly in cross-section of anotherembodiment of the apparatus of FIG. 1;

FIG. 4 is a plan view of the apparatus of FIG. 3; and

FIG. 5 is a schematic wiring diagram using the magnetic reed switchingapparatus in accordance with this invention.

In one embodiment of this invention, a magnetic reed switch includesfirst and second pole members positioned to be engaged by a magneticreed element which forms a movable switch arm. One or both of the polemembers form switch contacts. In one version of this embodiment, apermanent magnet is coupled between the pole members to bias the same toopposite polarity and to bias the reed element into contact with one ofthe pole members. A magnetic rotor having spaced alternating poles ofopposite polarity is then rotated so that the poles pass in sequence inclose proximity to the reed element to switch the same between the polemembers. In another version of the embodiment, a first permanent magnetis coupled between the pole members to bias the same to oppositepolarity, and a second permanent magnet is coupled to the reed elementto bias the same to a polarity opposite the polarity of one of the polemembers thereby biasing the reed element into contact with that polemember. A magnetic rotor having a plurality of spaced poles of the samepolarity is then rotated so that the poles pass in sequence past thereed element to move the element from the pole member to which it isbiased to the other pole member. After the pole passes the reed element,the element is once again biased by the permanent magnet back intocontact with the first pole member. The magnetic rotor of the firstversion of this embodiment includes a cylindrical, shaft driven magneticmember having relatively movable pole pieces mounted to oppositelypolarized end portions of the cylinder. A plurality of spaced poles oflike polarity are integral with each pole piece. The pole plates aremovable relative to one another to vary the spacing between the poles ofopposite polarity to control the time of operation of the reed element.The magnetic rotor of the second version of the embodiment is similar tothe first rotor, however, only one pole piece has spaced poles of likepolarity integral therewith. The pole piece and integral poles aremovable relative to the shaft to change the operation of the reedelement with respect to the shaft position.

Referring to the figures of the drawing, FIG. 1 shows magnetic reedswitch apparatus 10 which includes first and second pole members 12 and14 that extend through the glass envelope 16 of the switch. The polemembers are positioned in the envelope so that they may be engaged by areed element 18 which forms a movable switch arm. In this particularembodiment, a pool of mercury 20 is located in the bottom of theenvelope 16 and wets the reed element 18 so that it is able to withstandhigher currents than standard reed elements. A permanent magnet 22 iscoupled across the members 12 and 14 and biases them to oppositepolarities as indicated on the drawing. A second permanent magnet 24 iscoupled to the reed element 18 and biases that element to a south poleas indicated. A magnetic circuit is completed through the pole 12, andreed element 18 so that the element 18 is normally biased into contactwith pole member 12.

A magnetic rotor 26 includes a cylindrical magnetic member 28 which hasoppositely polarized end portions 29 and 30. Pole pieces 32 and 34 arefitted over the end portions of the magnetic cylinder 28 and contact theoppositely polarized portions. Therefore, the pole piece 32 ismagnetized as a north pole, and pole piece 34 is magnetized as a southpole. A shaft 36 imparts rotational movement to the magnetic rotor 26.In this embodiment it is not necessary to place a pole piece 34 over theend portion 30 of the magnetic member 28 but it may be desirable forasthetic purposes. Integral with the pole piece 32 and radiallyextending thereform are poles 38 which are radially spaced equidistantfrom each other. The pole piece 32 may he slipped around the magneticmember 28 so that the poles 38 may be moved relative to the shaft 36.

In operation, with the movement of the rotor 26 the poles 38 pass insequence in close proximity to the reed element 18 and accurately definea magnetic field which interferes with the magnetic field surroundingpole member 14. This temporarily changes pole member 14 from a southpole into a strong north pole, having a field stronger than the fieldsurrounding the pole member 12. In this condition, the reed element 18is attracted to the pole member 14 until the magnetic field defined bythe pole 38 has rotated past the pole member 14. Subsequently, the polemember 14 is once again magnetized as a south pole, and the member 18 isattracted back to the north pole member 12.

The rotor 41 of the magnetic switch apparatus in FIG. 3 is modifiedslightly from the rotor 26 of FIG. 1. In this version, a cylindrical,magnetic member 42 has a first pole piece 44 which is placed over themember 42 in contact with the end portion 45 which is magnetized as anorth pole. A second pole piece 46 is placed over the member 42 and isin contact with the end portion 48 of the member 42, which is polarizedas a south pole. Each of the pole pieces 44 and 46 have integral poles50 and 52 respectively radially spaced and radiating therefrom.

The pole pieces 44 and 46 are made to be movable about the shaft 54relative to each other. For instance, as shown in FIG. 4, the northpoles 50 are spaced 90 apart. The pole piece 46 also has the poles 52spaced 90 apart. By rotating the pole pieces 44 and 46 relative to oneanother the south poles 52 can be spaced at some angle X relative to thenorth poles 50.

Two pole members 54 and 55 are placed within a glass envelope 56 andpositioned so that they may 'be contacted by reed element 58 that servesas a contact arm. A permanent magnet 60 is coupled across the polemembers 54 and 55 and magnetizes them to north and south polesrespectively. As will be explained subsequently, with movement of therotor 40, the poles 50 and 52 pass in sequence in close proximity to thereed element 58 and accurately define a magnetic field cooperating withthe fields of the pole members for causing movement of the reed element58 between the .pole members 54 and 55.

A better understanding of the unique features of this magnetic switchingapparatus may be had by referring to the circuit diagram of FIG. 5. Thisdiagram shows a portion of the ignition system of an automobile. Inoperation, the ignition switch 62 is. closed coupling a potentialthrough ballast resistor 64, which does not have to be included in thecircuit in some applications and the reed switch apparatus 61 (whichrepresents both the apparatus 10 and the apparatus 40) to charge theprimary 59 of the ignition coil 66. When the switch 61 is open, the coil66 discharges inducing a potential in the secondary 68 of the coil 66.This potential is coupled to a distributor for distribution to the sparkplugs of the engine for firing the same. A capacitor 70 is placed in thecircuit across the magnetic switching apparatus 61 and serves to arrestthe spark upon the opening of the switch.

It is known to use a reed switching apparatus to replace the breakerpoints in an automobile ignition system such as has been described.However, in the past there has been a problem to get the switch to openat the desired time. Understanding of this problem may be had by adiscussion of FIGS. 3 and 4. In this figure both the pole members 54 and55 are used as contact terminals. By connecting a permanent bar magnet60 across the pole members 55 and 54, the reed element 58 will be biasedto one or the other of the pole members. If, for instance, the reedelement 58 was initially attracted to pole member 54, movement of rotor40 in a counterclockwise direction causes the magnetic field defined bythe north pole 50 to pass pole member 55, which is biased as a southpole. The field of pole 50 distracts the field of the pole member 55 tothe point that it attracts the reed element 58 from the north polemember 54.

During the time that the element 58 is in contact with the north polemember 54, the coil 66 is charging. As the north pole 50 passes the polemember 55, the element 5'3 moves to the pole member 55, opening thecircuit and permitting the coil 66 to discharge. This induces a voltagein secondary winding 68 to fire the engine. Subsequently the south pole52 approaches the pole member 55. Because pole member is a south pole,the field of pole 52 reinforces the field of member 55 so that theelement 58 remains in contact therewith, and the coil is charged. As thesouth pole 52 passes pole member 54, its field interferes with the fieldof pole member 54 to cause the reed element 58 to jump to pole member 54opening the switch and causing the coil 66 to discharge to fire anothercylinder of the engine. With the poles 50 and 52 being spaced 45 apartthere is a shorter switching time involved when a north pole passes thepole members 54 and 55 than when the south pole passes the members 54and 55 with the rotor being moved in a clockwise direction. This isbecause of the physical location of the pole members 54 and 55 inrelation to the rotating poles whereby the north pole 58 pass the polemember 55 with which field it cooperates for switching element 58 soonerthan the south poles 52 pass the pole member 54 with which field itcooperates to cause the switching action of element 58.

By making the pole pieces 44 and 46 movable relative to one another,however, it is possible to space the poles 52 closer than 45 from thepoles 50 so that they will pass by the pole member 54 at a point whichwill be apparently 45 from the north pole 50 but in reality might be 42or 43 degrees away from that pole. Because the pole pieces and integralpoles may be stamped from sheet material, formed and easily slipped overthe end portions of cylindrical member 42 in a movable relation withrespect to one another for spacing the integral poles, I have describeda simple and economic rotor that provides for proper ignition timing.

In the variation shown in FIG. 1, the rotor 26 has four north poles 38and could be used with 'a four cylinder internal combustion engine. Inthis embodiment, as was described, the element 18 is biased permanentlyto the pole member 12 and only this pole member acts as a switch contactfor the apparatus 10. The other pole member 14 simply acts as amechanical stop. When the rotor 26 is moved so that the poles 38 passthe pole member 14, the member 14 is biased to a north pole and attractsthe reed element switch arm 18 to open the switch 10. This causes thecoil 66 to discharge to fire one of the engine cylinders. After the pole38 passes the pole member 14, the reed element is biased back to polemember 12 by magnets 22 and 24 to close the switch 10, thereby chargingthe coil 66.

The shaft 36 of the rotor 26 is positioned with respect to thecrankshaft of the engine, and the pole piece 32 may be moved relative tothe shaft 36 to change the predetermined time of operation of the reedswitch element 18 with respect to the position of shaft 36, therebychanging the timing of the engine. Therefore, the switch 10 of FIG. 1 isopen at precisely the same time by each pole 38 so that the engine isfired with the proper timing.

What has been described, therefore is an improved magnetic reed switchapparatus wherein the reed element is switched at a constant rate byeach of the poles of the magnetic rotor and which is relativelyinexpensive to manufacture and assemble.

What is claimed is:

1. Magnetic switching apparatus including in combination, a magneticreed element forming a movable switch arm, first and second magneticpole members positioned to be engaged by said reed element and at leastone of said pole members forming a switch contact, permanent magnetmeans coupled to said magnetic pole members for biasing the same toopposite polarities, magnetic rotor means including a cylindricalmagnetic member having first and second oppositely polarized endportions, a shaft for supporting said cylindrical member and impartingmovement thereto, first and second pole pieces mounted on said ends ofsaid cylindrical member, one of said pole pieces having a plurality ofintegral radially spaced poles extending radially therefrom, said polespassing in sequence in close proximity to said reed element with themovement of said rotor and accurately defining a magnetic fieldcooperating with said pole members for causing predetermined movement ofsaid reed element, and said one pole piece being movable relative tosaid shaft of said rotor to change the predetermined time of operationof said reed element with respect to said shaft position.

2. The magnetic switching apparatus of claim 1 wherein said permanentmagnet means is further coupled to said reed element for biasing thesame into contact with one of said pole members, and wherein saidmagnetic rotor means includes a cylindrical magnetic member having firstand second oppositely polarized end portions, a shaft coupled to saidcylindrical member for driving the same, and at least one pole piecemounted on one end of said cylindrical member, said pole piece having aplurality of integral radially spaced poles extending radiallytherefrom.

3. The magnetic switching apparatus of claim 2 wherein said pole pieceis movable relative to said shaft of said rotor to change thepredetermined time of operation of said reed element with respect tosaid shaft position.

4. Magnetic switching apparatus having a reed element operable bychanging magnetic fields including in combination, magnetic rotor meanshaving first and second oppositely polarized portions, first and secondrelatively movable pole pieces mounted to said rotor means and eachcontacting a respective one of said oppositely polarized portions, aplurality of spaced poles of like polarity integral with each polepiece, said poles alternately passing in close proximity to the reedelement and defining a changing magnetic field for operating the same,said first and second pole plates being movable relative to one anotherto vary the spacing between said poles of opposite polarity therebyvarying the frequency of the changing magnetic field to control theoperation of the reed element.

5. The magnetic switching apparatus of claim 4 wherein said magneticrotor includes a cylindrical magnetic member having first and secondoppositely polarized end portions and a shaft coupled to the member fordriving the same, and said pole pieces are mounted to said oppositelypolarized end portions with said poles integral with each of said polepieces being radially spaced and extending radially therefrom, said polepieces being movable relative to one another to vary the spacing betweensaid poles of opposite polarity.

6. In an ignition system for an internal combustion engine having anignition coil and distributor, the combination including magneticswitching apparatus for controlling the current through the ignitioncoil, the switching apparatus including in combination, a magnetic reedelement forming a movable switch arm, first and second magnetic polemembers positioned to be engaged by said reed element and at least oneof said pole members forming a switch contact for applying a potentialto the coil to charge the same, magnet means coupled to said magneticpole members for biasing the same to opposite polarities, magneticrot-or means including a cylindrical member having first and secondoppositely polarized end portions, a shaft for supporting saidcylindrical member and parting movement thereto, first and second polepieces mounted on said ends of said cylindrical member, one of said polepieces having a plurality of integral radially spaced poles extendingradially therefrom, said poles passing in sequence in close proximity tosaid reed element with the movement of said rotor and accuratelydefining a magnetic field cooperating with said pole member for causingpredetermined movement of said reed element to open and close saidswitch contact thereby discharging and charging the ignition coilrespectively, and said one pole piece being movable relative to saidshaft of said rotor to change the predetermined time of operation ofsaid reed element with respect to said shaft position thereby changingthe ignition timing of the engine. 1

References Cited UNITED STATES PATENTS 3,284,740 11/1966 Neapolitakis335-153 3,291,106 12/1966 Neapolitakis 123-448 BERNARD A. GILHEANY,Primary Examiner.

R. N. ENVALL, 111., Assistant Examiner.

4. MAGNETIC SWITCHING APPARATUS HAVING A REED ELEMENT OPERABLE BYCHANGING MAGNETIC FIELDS INCLUDING IN COMBINATION, MAGNETIC ROTOR MEANSHAVING FIRST AND SECOND OPPOSITELY POLARIZED PORTIONS, FIRST AND SECONDRELATIVELY MOVABLE POLE PIECES MOUNTED TO SAID ROTOR MEANS AND EACHCONTACTING A RESPECTIVE ONE OF SAID OPPOSITELY POLARIZED PORTIONS, APLURALITY OF SPACED POLES OF LIKE POLARITY INTEGRAL WITH EACH POLEPIECE, SAID POLES ALTERNATELY PASSING IN CLOSE PROXIMITY TO THE REEDELEMENT AND DEFINING A CHANGING MAGNETIC FIELD FOR OPERATING THE SAME,SAID FIRST AND SECOND POLE PLATES BEING MOVABLE RELATIVE TO ONE ANOTHERTO VARY THE SPACING BETWEEN SAID POLES OF OPPOSITE POLARITY THEREBYVARYING THE FREQUENCY OF THE CHANGING MAGNETIC FIELD TO CONTROL THEOPERATION OF THE REED ELEMENT.